Magnetron beam tube circuit



Feb. 2, 1965 A. SOMLYODY 3,158,674

MAGNETRON BEAM TUBE CIRCUIT Filed March 8, 1960 O 'I' 2 "9" w2 24 FLIP 35 FLOP I-1 37 Z IN V EN TOR.

' ,gRPAD SOMLYODY mam A T TORNE Y the cathode.

United States Patent Ofiice 3 ,168,674 Patented Feb. 2, 1965 3,168,674 MAGNETRON BEAM TUBE CIRCUIT Arpad Somlyody, Raritan, N.J., assiguor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Mar. 8, 1960, Ser. No. 13,476

3 Claims. (Cl. 315-8.5)

This invention relates to pulse generating circuits and particularly to circuits for generating pulses for clearing and resetting a beam switching tube.

A magnetron-type beam switching tube includes a central cathode and a plurality of groups of electrodes surrounding the cathode, to each of which an electron beam flows and from each of which an output signal may be obtained. Generally, each group of electrodes includes a spade electrode which serves to form and hold an electron beam, a target electrode associated with each spade electrode and adapted to receive the beam, and a switching grid electrode which is adapted to switch an electron beam from one position to the next. In operation of a tube of this type, for example in a counter circuit, after the tube has executed a predetermined counting operation, it is desirable to clear the electron beam from the group of electrodes to which it may be flowing and then reset the beam at a selected zero position. There are many circuits available for performing this operation. However, the present invention difiers from these known circuits in being characterized by its simplicity, in not using tubes, transistors, or other similar active elements, and in other desirable features of operation which will appear as the invention is described below.

The principles and objects of the invention are directed toward the provision of an improved and comparatively simple circuit for generating two time-related pulses which are particularly suitable for use in clearing and resetting an electron beam in a magnetron-type beam switching tube, the circuit providing both clear and reset pulses without using tubes, transistors, or similar active elements.

In brief, the circuit of the invention includes two circuit loops each comprising only impedance elements with a common coupling impedance between the loops. One loop of the circuit provides a pulse for clearing a beam switching tube, and the other loop provides a pulse for resetting the beam at the selected zero position. Switching means is provided for first charging the circuit and preparing it for producing the desired clear and reset pulses. When the switching means is properly actuated, current flows though the first loop, passes through an inductor and thereby generates the desired clear pulse. This same current passing through the common coupling impedance generates a pulse in this impedance which is transmitted along a delay line included in the second loop to the output of the loop where the reset pulse appears. The delay line is designed to provide the desired time interval between the appearance of the clear pulse and the reset pulse at the appropriate output terminals from which they are applied to the beam switching tube.

The invention is described in greater detail by reference to the single figure of the drawing which is a schematic representation of a circuit embodying the invention.

The circuit de cribed below is particularly suited for use with a multiposition type 6700 magnetron beam switching tube. In actual construction, this type of tube is cylindrical in form but is shown schematically in linear form as tube in the drawing. The tube includes an envelope 12 which contains a central longitudinally elongated cathode 14 and ten groups of electrodes spaced radially equidistantly from the cathode and surrounding For simplicity, only four groups of electrodes are shown numbered 0, l, 2, and 9. Each group of electrodes includes a generally U-shaped elongated spade electrode 16 and a generally L-shaped target electrode 18 positioned so that each target: occupies the space between adjacent spade electrodes. Each spade electrode serves to form and hold an electron beam on its corresponding target electrode. Agenerally rod-like switching electrode 20 is also included in each group of electrodes and is positioned between one edge of each target electrode and the adjacent spade electrode. The switching electrodes are known as switching grids. An open-ended cylindrical permanent magnet 22 is provided surrounding the tube envelope and coaxial therewith. The magnet provides an axial magnetic field which is utilized in conjunction with electric fields within the tube to form and switch an electron beam from the cathode to each of the groups of electrodes. The direction in which the beam switches, that is clockwise or counterclockwise, is always the same and is determined by the orientation of the electric and magnetic fields.

Briefly, in operation of tube 10, electrons emitted by the cathode are retained at the cathode if each of the spades, targets and switching grids carries its normal operating electrical potential. When a spade experiences a suitable lowering of its potential, an electron beam is formed and directed to the corresponding target electrode. The electron beam may be switched from one target electrode to the next by suitably altering the electrical potentials of a spade or switching grid. Under normal operating conditions, whenever electrode voltages are such that a beam might be supported at several positions, the beam will switch to the most leading position and lock in at this position.

In the circuit shown, the cathode 14 is connected through a suitable resistor 24 to ground. Each of the spade electrodes 16 is coupled through a spade load resistor 26 to a spade buss 28. The spade buss 28 is coupled through a common spade resistor 30 to a positive DC. power supply V of about 200 volts.

The target electrodes 18 are connected through suitable load resistors 34 to a common target buss 36 which is coupled to a positive DC. power supply V; of about 300 volts. In addition, an auxiliary output tap 38 is provided at eachtarget for connection to a utilization device or circuit, if desired. Thus, the target electrodes 18 of the tube 10 may be connected, for example to the glow cathodes of an indicator tube such as the type 6844 tube, or to a printing mechanism or the like.

The switching grid electrodes 20 are connected in two sets with the grids at the even-numbered positions in one set and the grids at the odd-numbered positions in another set. The sets of grids are connected by leads 35 and 37 to the outputs of a suitable flip-flop circuit 38. Suitable input signals are applied over lead 39 to the input of the flip-flop, and as one and then the other output of the flip-flop operates, a beam is moved from position to position in the tube 10. i

The pulse-producing circuit 40 of the invention which provides clear and reset pulses for the tube 10 includes a first loop which has a first current flow path comprising two resistors 41 and 42 connected between power supply V and ground. The junction point 43 of resistors 41 and 42 is coupled through capacitor 44 to the cathode 14 of tube 10. An inductor 45 and resistor 46 are connected across resistor 42 with a diode 47 connected between the junction point 43 and the high end of inductor 45, the anode of the diode being connected to the inductor and the cathode of the diode being con nected to junction 43. The junction point 48 of the diode 47 and inductor 45 is connected to one terminal 49 of a two-way switch 50, the second terminal 51 of which is coupled through resistor 52 to power supply V The switch also includes a movable arm 53 connected to common terminal 54 which is coupled through capacitor .3 55 and resistor 56 to ground. A resistor 57 and capacitor 58 are connected across the switch 50 to protect it during operation.

The circuit 40 also has a second loop which includes the resistor 56 as a common coupling element between the two current flow loops. The common resistor 56 feeds into a suitable delay line 65 comprising an inductor 66 connected between a pair of capacitors 68 and70 which are in parallelwithresistor 56. The delay line is selected to provide a suitable delay between pulses generated by the two loops of the circuit 40. The delay line 65 is coupled to the cathode of a diode 72, the anode of which is coupled through resistor 73 to ground. The junction point 74 of diode 72 and resistor 73 is connected by lead 76 to the resetportion (not shown) of flip-flop 38. Junetion point 74 is also coupled by capacitor 77 to the spade electrode 16 at the position of tube 10.

In operation of the invention, assume that the tube has executed a predetermined counting operation by means of switching an electron beam from position to position, and itis now desired to clear the beam and reset it at the zero position. Intially, the movable arm 53 of the switch 50 is in contact with terminal 51 so that current flows from the power supply to the capacitor 55 which is charged thereby. Now, to perform the clearing and resetting operation, the arm 53 is moved into contact with terminal 49, and the capacitor 55 discharges through the inductor 45 and resistor 46. This pulse of discharge current provides the positive clear pulse 80 of about 200 volts at the junction 43. The pulse 80 is applied to the cathode 14 of tube 10 and raises the potential of the cathode to such a level that an electron beam in the tube is cleared. At the same time, the discharging current from the capacitor 55 which also flows through the resistor 56 also generates a voltage pulse across this resistor. This pulse travels down the delay line and appears at the junction, 74 as negative pulse 82 of about 200 volts which is applied to the spade 16 at the 0 position. This pulse lowers the potential of this spade below that of all of the other spades and an electron beam forms at the 0 position.

The inventionas thus described provides essentially one circuit for generating two pulses, the circuit being simple, inexpensive and using no active circuit elements such as tubes, transistors or the like, Thebasic principles of the invention are clear from the foregoing discussion, and

modifications thereof to satisfy specific circuit requirements will be readily apparent to those skilled in the art. For example, the amplitude of the pulses generated by the circuit may be readily varied, and, in addition, the time delay between the pulses may be varied as required.

What is claimed is:

1. A circuit for clearing and resetting an electron beam in a magnetron beam switching tube including an electron beam switching tube having a cathode and a plurality of groups of electrodes; each group including a target electrode which receives an electron beam and produces an output signal therefrom, a spade electrode which holds an electron beam on its associated target electrode, and a switching electrode which serves to switch an electron beam from one group of electrodes to the next; and magnet means for providing a longitudinal magnetic field for said electrodes; a first circuit loop for generating a first pulse; a second circuit loop for generating a second pulse; a common coupling impedance between said circuit loops, said first and second circuit loops including only resistive, capacitive :and inductive elements; first output means coupled between said first circuit loop and the cathode of said tube; and second output means coupled between said second circuit loop and one of the groups of electrodes in said tube.

2. The circuit defined in claim 1 wherein said first loop includes a capacitor, means for charging said c-apacitor, an inductor, and means for discharging said capacitor through said inductor; and said second loop includes time delay means for controlling the time relationship between said first and second pulses.

3. The circuit defined in claim 1 wherein said first output means is adapted to apply a beam clearing pulse to said cathode and said second output means is coupled to a selected spade electrode in said beam switching tube for applying a beam forming pulse thereto.

References Cited in the file of this patent UNITED STATES PATENTS 2,487,602 Schoenfeld Nov. 8, 1949 2,808,535 Lee Oct. 1, 1957 2,927,242 Schultz Mar. 1, 1960 3,001,137 Kassel et a1. Sept. 19, 1961 3,034,062 Bleam May 8, 1962 

1. A CIRCUIT FOR CLEARING AND RESETTING AN ELECTRON BEAM IN A MAGNETRON BEAM SWITCHING TUBE INCLUDING AN ELECTRON BEAM SWITCHING TUBE HAVING A CATHODE AND A PLURALITY OF GROUPS OF ELECTRODES; EACH GROUP INCLUDING A TARGET ELECTRODE WHICH RECEIVES AN ELECTRON BEAM AND PRODUCES AN ELECTRON SIGNAL THEREFROM, A SPADE ELECTRODE WHICH HOLDS AN ELECTRON BEAM ON ITS ASSOCAITED TARGET ELECTRODE, AND A SWITCHING ELECTRODE WHICH SERVES TO SWITCH AN ELECTRON BEAM FROM ONE GROUP OF ELECTRODES TO THE NEXT; AND MAGNET MEANS FOR PROVIDING A LONGITUDINAL MAGNETIC FIELD FOR SAID ELECTRODES; A FIRST CIRCUIT LOOP FOR GENERATING A FIRST PULSE; A SECOND CIRCUIT LOOP FOR GENERATING A SECOND PULSE; A COMMON COUPLING IMPEDANCE BETWEEN SAID CIRCUIT LOOPS, SAID FIRST AND SECOND CIRCUIT LOOPS INCLUDING ONLY RESISTIVE, CAPACITIVE AND INDUCTIVE ELEMENTS; FIRST OUTPUT MEANS COUPLED BETWEEN SAID FIRST CIRCUIT LOOP AND THE CATHODE OF SAID TUBE; AND SECOND OUTPUT MEANS COUPLED BETWEEN SAID SECOND CIRCUIT LOOP AND ONE OF THE GROUPS OF ELECTRODES IN SAID TUBE. 